A general magnetic-energy-based torque estimator: validation via a permanent-magnet motor drive

This paper describes the use of the current–flux-linkage ($i{-}psi$ ) diagram to validate the performance of a general magnetic-energy-based torque estimator. An early step in the torque estimation is the use of controller duty cycles to reconstruct the average phase-voltage waveform during each pulsewidth-modulation (PWM) switching period. Samples over the fundamental period are recorded for the estimation of the average torque. The fundamental period may not be an exact multiple of the sample time. For low speed, the reconstructed voltage requires additional compensation for inverter-device losses. Experimental validation of this reconstructed waveform with the actual PWM phase-voltage waveform is impossible due to the fact that one is PWM in nature and the other is the average value during the PWM period. A solution to this is to determine the phase flux-linkage using each waveform and then plot the resultant $i{-}psi$ loops. The torque estimation is based on instantaneous measurements and can therefore be applied to any electrical machine. This paper includes test results for a three-phase interior permanent-magnet brushless ac motor operating with both sinusoidal and nonsinusoidal current waveforms

Analytical and numerical computation of air-gap magnetic fields in brushless motors with surface permanent magnets

This paper extends the theory of the air-gap magnetic field in permanent-magnet (PM) brushless motors. Scalar and vector potential solutions to the field equations are brought together to unify many of the important practical methods already in use. The theory admits a more general representation of the magnetization vector than has been previously assumed, including both the radial and tangential components, and variation with radius. The work is applied in the design of PM motors where there is a requirement to minimize noise and torque ripple, and maximize efficiency, and a continuing need for improvements in the accuracy and rigor of design calculations. The air-gap flux-density distribution is at the heart of the design process, and it is desirable to study different magnetization patterns, including imperfections in the magnetization, for a wide range of magnet shapes. This paper shows the application of the analytical solutions in comparison with a new finite-element procedure, with test results on a prototype motor, and with simpler, older methods of calculation based on magnetic equivalent circuits. The comparison brings out many interesting points in relation to the accuracy and the speed and practicality of the various methods

Embedded finite-element solver for computation of brushless permanent-magnet motors

This paper describes the theory underlying the formulation of a “minimum set” of finite-element solutions to be used in the design and analysis of saturated brushless permanent-magnet motors. The choice of finite-element solutions is described in terms of key points on the flux–MMF diagram. When the diagram has a regular shape, a huge reduction in finite-element analysis is possible with no loss of accuracy. If the loop is irregular, many more solutions are needed. This paper describes an efficient technique in which a finite-element solver is associated with a classical $d$– $q$-axis circuit model in such a way that the number of finite-element solutions in one electrical half-cycle can be varied between 1 and 360. The finite-element process is used to determine not only the average torque but also the saturated inductances as the rotor rotates

The psychosocial impact of vaginal delivery and cesarean section in primiparous women

The aim of this study was to identify how the method of delivery and birth experience interfere with maternal psychological status early after puerperium. We conducted a prospective study on 148 women after puerperium from November 2017 to January 2018 in Bucur Maternity Hospital. Women that delivered vaginally mobilized in the first 6 hours in 73.7% of the cases, but for cesarean section after 12- 24 hours in 43.6% of the cases. Women described good support from the obstetrician in 58.1% of the cases. 90.5% of the women reported that the method of delivery did not have an impact on infant care and 73% had no lactation problems. The majority described little trauma, in 32.4% of the cases. 70.3% of the patients reported that they wanted to have more children and 59.5% of them desired the same method of delivery. Negative feelings, lactation, and taking care of the baby were not influenced in this study by the method of delivery, but by prematurity of birth and the complications that women experienced at birth

EFFECTS OF INTERACTION BETWEEN ABIOTIC STRESS AND PATHOGENS IN CEREALS IN THE CONTEXT OF CLIMATE CHANGE: AN OVERVIEW

The scenario that climate change will lead to higher incidence of crop diseases, following geographical distribution of the host and cropping technology, suggests that can be positive, negative or neutral depending of multiple interactions between host, pathogens and abiotic stress factors. Both plants and pathogens are constantly threatened by abiotic stress factors such as high temperature, moisture, drought, salinity, soil pH, greenhouse gases, Ultraviolet-B (UVB) radiation and air pollutants. Currently the research focused on this topic is inconsistent therefore these interactions are poorly understood. In the process of adaptation to these adverse conditions, it is expected that abiotic stress factors impact pathogens into a wide range of responses such as changes in life cycles (pathogen reproduction – shorter incubation -, dispersal, survival and activity), increased incidence, modified pathogenicity, genetically recombination and aggressiveness traits.  The present review is focused particularly on the impact of abiotic stress factors on cereals pathogens and all changes in their life cycles and host-pathogen interaction associated with under climate change conditions. However, our study suggest that a better understanding of interaction between pathogens and abiotic stress factors can be an important mechanism to estimate disease risk on a large scale and to introduce new understandings in developing management strategies

Determination of pyrrolizidine alkaloids in dietary sources using a spectrophotometric method

Pyrrolizidine alkaloids (PAs) are a class of toxic compounds found in the composition of more than 6000 plants. People can be exposed to PAs by consuming phytotherapeutic products, food from crops contaminated with seeds of some species with high content of PAs, and/ or contaminated animal products like bee products. For this reason we developed and validated a method for quantitative determination of PAs, from the most frequently contaminated food sources, honey and flour. Colorimetric Ehrlich reagent method was used with standard addition (1mg/kg senecionine). The extraction solvent was methanol 50% acidified with citric acid to pH 2-3, as this solvent can be used for alkaloids and N-oxides. We found that, in extracting the alkaloid only once from the dietary sources, the percent of recovery is low (52.5% for honey, and 45.75% for flour). Using successive extractions, three times with the same solvent, the senecionine retrieval percentage increased to 86.0% for honey and 76.0% for flour. The method was validated using the following parameters: selectivity, linearity (0,25- 20 mg/ mL senecionine), accuracy (average recovery 93.5 - 107.93%) and precision (RSD 3,26-4.55%.). The calculated limit of quantification (0.174 mg/ mL) makes this method applicable for determining Pas occurring at toxic levels for consumers

Set-valued observer-based active fault-tolerant model predictive control

This paper proposes an integrated actuator and sensor active fault-tolerant model predictive control scheme. In this scheme, fault detection is implemented by using a set-valued observer, fault isolation (FI) is performed by set manipulations, and fault-tolerant control is carried out through the design of a robust model predictive control law. In this paper, a set-valued observer is used to passively complete the fault detection task, while FI is actively performed by making use of the constraint-handling capability of robust model predictive control. The set-valued observer is chosen to implement fault detection and isolation (FDI) because of its simple mathematical structure that is not affected by the type of faults such as sensor, actuator, and system-structural faults. This means that only one set-valued observer is needed to monitor all considered actuator and sensor statuses (health and fault) and to carry out the fault detection and isolation task instead of using a bank of observers (each observer matching a health/fault status). Furthermore, in the proposed scheme, the advantage of robust model predictive control is that it can effectively deal with system constraints, disturbances, and noises and allow to implement an active FI strategy, which can improve FI sensitivity when compared with the passive FI methods. Finally, a case study based on the well-known two-tank system is used to illustrate the effectiveness of the proposed fault-tolerant model predictive control scheme.Peer ReviewedPostprint (author's final draft